A Research of the Influence of Variable Intersection Angles between Tunnels to the Stability of Underground Excavated Chambers in Rock Masses using Key Block Theory

[[abstract]]地下廠房能夠有效地增加使用空間的用途於倉庫、工業操作、發電、軍事防護、礦採、及其他目的等，而且其使用優點包括不易受到山崩、暴風雨或地震之傷害、廠房內可保持常溫及常濕狀態、可抗拒物理、化學及高載重之風化環境。雖然，地下空間之使用比地上空間更具有經濟效益，但是其有效性必仍然必須相當地依賴於岩塊的節理系統。 從三維網路的配置選擇去了解最經濟的地下空間開挖，標準在於最少量的人工支撐為主。在一自立支撐的地下開挖，應力的初始狀態將因岩體的被挖除以及節理平面的互鎖行為而產生集中的現象。原先整體性塊體的結構會因關鍵塊體(key block)的失去平衡而引起連鎖的移動效應，依序地產生移動而影響其穩定性。關鍵塊體理論(Key Block Theory)對位態、形狀及開挖的配置可提供最佳化選擇以減低塊體受開挖時產生移動而造成施工的危險 本研究延續明潭地下電廠成功地應用關鍵塊體理論之成果，再針對明潭地下電廠廠房於不同交叉段之走向對節理岩盤穩定性之影響。研究成果顯示地下廠房交叉段走向之選擇會深深地影響潛在關鍵塊體的滑動形式、數目及大小，另外本研究也提供分析結果以決定最佳之選線方向而可增加岩石開挖的安全性同時可減少支撐。[[abstract]]Using underground space is an effective manner to increase the operation room for storage, industrial operation, power generation, military defense, mining, and other purposes. Its advantages include the facility’s invulnerability to landslides, storms, or earthquakes and the capability to keep constant temperature and humidity in the space and high resistance to physical, chemical, or thermal loads as well. Although the underground space could more economically provide profits than the surface ground, the effectiveness of using underground space should rely on the joint system in rocks. One of the most economical ways to arrange the underground space is to choose an arrangement from the three dimensional excavation networks that requires only the minimal artificial rock support. In a self-supporting underground opening, the initial state of stress should be concentrated due to the opening of the jointed rocks and the interlocking of joint sets. The original stability of the jointed rock system will be affected by the balance loss of the key blocks resulting in the sequential movements of the other rock blocks. Key Block Theory could provide the optimum choices for the orientations, shapes, and arrangements of the openings of rocks to minimize the danger of block movements. Shapes, and arrangements of openings to minimize the danger of block movements. The previous successful research of applying the Key Block Theory to the block stability analysis of Mintan underground electrical power plant is continued in this research in order to investigate the influence of the variable intersection angles between tunnels to the stability of underground excavated chambers in rock masses. The research result demonstrates that the choice of direction for the intersection dimension of an underground chamber would greatly influence the type, numbers, and size of potential key blocks and shows the optimum selection for the direction of a chamber in order to increase the safety of the rock system and reduce the rock supports